Hindawi Publishing Corporation International Journal of Zoology Volume 2011, Article ID 598504, 10 pages doi:10.1155/2011/598504

Research Article Reproductive Traits of Some Amphipods (Crustacea: ) in Different Habitats of Iran and Southern Caspian Sea

Alireza Mirzajani,1 Mostafa Sayadrahim,1 and Alireza Sari2

1 Department of Ecology, Inland Water Aquaculture Research Center, P.O. Box 66, 43167 Guilan, Iran 2 School of Biology, University College of Science, University of Tehran, 14155 Tehran, Iran

Correspondence should be addressed to Alireza Mirzajani, ar [email protected]

Received 20 December 2010; Revised 16 February 2011; Accepted 12 April 2011

Academic Editor: Chris Lloyd Mills

Copyright © 2011 Alireza Mirzajani et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Reproductive traits of seven amphipods from northern parts of Iran at 11 localities were studied in order to find feasible species for usage in aquaculture industries. The results revealed that the breeding season for lacustris and G. paricrenatus from high latitudes was limited to a few months from May to June. Breeding activity of G. komareki from some springs was observed throughout the year, while Obesogammarus acuminatus and G. aequicauda from southern wetlands of the Caspian Sea and Pontogammarus maeoticus and P. borceae from southern Caspian sea shore showed various patterns. The mean egg number of O. acuminatus and G. aequicauda species was the highest with 49.8 and 37.7, respectively, while this value for G. komareki and P. maeoticus was the lowest with an average of 8.8 eggs. Reproductive strategy was found to be related to habitat characteristics such as chemical factors, substrate status, and the epifaunal living.

1. Introduction of Nelson [3], Kolding and Fenchel [4], and Sainte-Marie [5] are informative about reproductive patterns. According to Amphipods are often selected as test organisms in different Sainte-Marie [5] life histories of gammarideans fall into eight studies because of their widespread distribution, sensitivity categories. Most of them are an iteroparous annual type; the to disturbance, and culture suitability [1]. Introduction of high reproductive potentials were described for semiannual macroinvertebrates such as to fish culture ponds populations in low latitude habitats while low reproductive has been used to improve fish diet, and many amphipods potentials were more frequent in perennial gammarideans at have been used [2]; others can be found in the website high latitudes. (http://www.elacuarista.com/). Amphipod adaptation and During a project [6] to find suitable species of amphipods continuous reproduction in the new environment are the for aquaculture industries, the reproductive traits of Am- main factors for success. phipoda were examined in different habitats from the north- A wide variation in reproductive parameters is found ern part of Iran. The selected species were Gammarus lacus- within amphipods, correlated with a wide variety of micro- tris G. O. Sars, 1863, G. paricrenatus Stock et al. 1998, G. habitat conditions. A wide variation in reproductive parame- komareki Schaferna,˜ 1992, G. aequicauda Martynov, 1931, ters is found within amphipods corresponding to diversity of Obesogammarus acuminatus Stock et al. 1998, Pontogam- microhabitats conditions. In this regard, many comparisons marus maeoticus (Sowinsky, 1894), and P. borceae (Carausu, of reproductive traits were explained by Nelson [3]forbrack- 1943) from Iranian inland waters and southwest coast of the ish water versus freshwater and marine, single-brooded ver- Caspian sea. All species had been confirmed previously by sus multiple-brooded, and infaunal versus epifaunal species. Stock et al. [7]. It was important to investigate their life cycle However, an extensive literature has been published on the and breeding season in their respective habitats as reproduc- biology and life cycles of different amphipods; the studies tive traits vary with local water environment parameters. 2 International Journal of Zoology

has been described as a new species [7]. On the other hand no specimens of Obesogammarus acuminatus were found in Anzali Wetland for a few months. The sampling was conducted by an Ekman dredge for

Caspian sea muddy substrate or by a handle sieve (0.125 mm screen) for the aquatic vegetation and sandy substrates. The were washed from debris and preserved in 75% alcohol. In the laboratory, the length of the was measured to the nearest 1 mm from the anterior head margin to the posterior Caspian sea margin of the telson with a stereomicroscope fitted with a H Astara graticule. Animals were classified into five groups. Sex deter- 38 N mination was according to the presence of oostegites. Breed- N Sefid Rud estuary ing periods, clutch sizes, and ovigerous females percentage determined the breeding activity during the year. Juveniles Kelachi in the brood pouch were assessed separately. The sex ratio S was calculated for adults (longer than eight mm), and the t K mean length of adults was compared for each sex using a - test. For multiple comparison of means ANOVAwas used for some data analysis. Some environment characteristics such 36 N 52 E 54 E as hydrochemical parameters were measured by standard 48 E 50 E methods [16] to show the habitats variation.

Anzali Wetland Gorgan Bay 3. Results Neur Lake Gorigol Wetland Biometric results showed a significant difference between the Caspian sea shore mean length of males and females where in most species Spring (H: Hiran N: Navrud males were longer than females, although Pontogammarus S: Sefidab K: Kojor) maeoticus was larger than males (Table 2). The sex ratios were Figure 1: Sampling localities in northern parts of Iran. highly variable for all species during the year while in the adult stage the male dominated. In P. borceae the sex ratio was 1 : 1.1, 1 : 1.2 for G. paricrenatus, G. komareki, G. aequicauda, 2. Study Area and Methods O. acuminatus and 1 : 2.2 for P. maeoticus (Table 2). The length-frequency histogram (Figure 2)ofGammarus Different features of reproduction were studied in seven lacustris shows that newly hatched (<4 mm long) individuals Amphipoda species from 11 habitats in the northern part dominate with 43% and 23% of the population in June and of Iran (Table 1, Figure 1) mostly from the Caspian drainage July (Figure 3), respectively. They grow during the following basin. On the Iranian coast of the Caspian Sea Pontogam- months to juveniles with lengths of 4–8 mm, and their marus maeoticus is the most abundant and widely distributed frequency in the population was 38% to 65% during August [8], and P. borceae is much less abundant [9], both of which and October, respectively. The larger specimens (>12 mm) are considered in this study. Generally P. maeoticus inhabits constituted the highest abundance in April and May with the sublittoral region and is known from the Pontic and Azov 84% and 37%, respectively. The newly hatched (<4mmlong) Sea basins [10]whileP. borceae has already been identified individuals of G. paricrenatus (Figure 3) dominated in May– from the Pontic area with rheophilous characteristics [11]. July and comprised 30% to 49% of the population. They Gammarus komareki from small streams and springs is the grow during the following months as the juveniles (4–8mm most common freshwater gammarid [7, 12] in the northern long) make up 65% of the population during August. The part of Iran. It is also distributed in Bulgaria, the northern larger specimens (>12 mm) show the highest frequency of part of Greece and Turkey, and around the Black sea [12]. At 72% in March (Figure 2). The maximum mean length was the south east of the Caspian sea in Gorgan Bay the common observed in May and the minimum in June (Figure 4). Mediterranean species G. aequicauda introduced to Caspian Studies on G. aequicauda Martynov, 1931 (Figure 2) water before 1994 [13] is also considered. revealed that newly hatched (<4 mm long) individuals The specimens were collected monthly from April 2001 present all year round while the frequency of juvenile (4– to March 2002, though a few samples were missed in Neur 8 mm long) in the population was more than 50% (Figure 3). Lake and Gorigol Wetland due to heavy snow and ice The larger specimens (>12 mm) constituted only 20 to 30% coverage of the Lake. Stock et al. [7]reportedG. lacustris in of the population in most periods, and the largest specimen Neur Lake and many other sites, previously recorded from was 19 mm in length. Iran [14]. This species is widely distributed throughout the Length-frequency histograms of O. acuminatus revealed world and prefers mountain and glacier Lakes as habitats that newly hatched and juvenile (<8 mm long) individu- [12, 15]. In the Gorigol Wetland, Gammarus paricrenatus als were present in all sampling periods (Figure 3)when International Journal of Zoology 3

19 55 17 150 93 47 5 39 44 85 15 13 11 No specimens 9 7 5 3 1 17 134 134 32 15 50 200 137 42 104 18 133 88 13 143 11 9 7 5 3 1 20020200 20 30 0 3025525 5 10 0 10 30 0 30 255525 10 0 10 10 0 10 25552520 0 20 20 0 20 11 229 222 119 166 105 246 177 161 14 260 151 9 164 7 5 3 1

11 125 167 84 47 73 9 25 29 70 101 111 75 7 5 3 1

11 301 250 296 297 270 310 119 425 235 227 9 165 97 7 5 3 1

17 264 137 243 166 103 128 117 15 Without sampling 13 11 9 7 5 3 1 15 13 314 306 150 113 11 33 253 173 123 9 7 5 Without sampling 3 1 G. paricrenatus G. lacustris G. komareki P. borceae P. maeoticus G. aequicauda O. acuminatus 30030 35 0 3530 0 30 30 0 30 35 0 3540040 30 0 3015 0 15 30 0 30 35 0 35 30 0 30 30 0 30 Frequency Frequency Frequency Frequency Frequency Frequency Frequency Frequency Frequency Frequency Frequency Frequency Apr. 2001 May 2001 Jun. 2001 Jul 2001 Aug. 2001 Sep. 2001 Oct. 2001 Nov. 2001 Dec. 2001 Jan. 2002 Feb. 2002 Mar. 2002

Unsexed Male and female

Figure 2: Size and sex composition of studied species during April 2001 to March 2002. The numbers examined are circled.

60 the larger specimens (>12 mm) had the least frequency. The maximum and minimum mean length was observed in May 50 and June, respectively, (Figure 4). The newly hatched and < 40 juvenile ( 6 mm long) individuals of P. maeoticus (Figure 2) dominated in most of the months (from 24 to 76% of the 30 population). The maximum mean length was observed in (%) May and the minimum in October (Figure 4). Individuals 20 of P. borceae less than 6 mm long (Figure 2) were recorded throughout the year while the large specimens (>9 mm) 10 were dominant in spring and winter (from 16 to 38% of 0 the population). The maximum mean length was recorded in May and the minimum in January (Figure 4). ff

Jul-01 There was a significant di erence in mean length during Jan-02 Jun-01 Sep-01 Feb-02 Oct-01 Apr-01 Dec-01 Aug-01 Mar-02 Nov-01 May-01 the year for all species (Figure 4), and according to Figure 3 G. lacustris G. paricrenatus the peak of abundance of newly hatched and juvenile length G. aequicauda O. acuminatus classeswasinMaytoJulyforG. lacustris and G. paricrenatus G. komareki P. maeoticus P. borceae while other species showed various patterns during the year. Furthermore the greatest percentage of ovigerous females of Figure 3: The newly hatched and juvenile (<4 mm long) individuals G. lacustris was observed in May 2001 while it was in April for each species during April 2001 to March 2002. for G. paricrenatus (Figure 4). 4 International Journal of Zoology

18 25 100 F = 75.33, df = 7 15 20 80 12 15 60 9 10 40 6 Length (mm) G. paricrenatus Egg (num/ind.) 5 20 3 Ovigerous female (%)

0 0 0 AM J J A S OND J FM AM J J A S OND J FM 2001 2002 2001 2002 18 18 100 F = 154.07, df = 6 16 15 14 80 12 12 60 10 9 8 40 G. lacustris 6 6 Length (mm) Egg (num/ind.) 4 20 3 Ovigerous female (%) 2 0 0 0 AM J J A S OND J FM AM J J A S OND J FM 2001 2002 2001 2002 12 21 100 = . = F 15 75, df 11 18 10 80 8 15 12 60 6 9 40 4 G. komareki

Length (mm) 6 Egg (num/ind.) 20 2 3 Ovigerous female (%) 0 0 0 AM J J A S OND J FM AM J J A S OND J FM 2001 2002 2001 2002 12 60 100 F = 26.97, df = 10 10 50 80 8 40 60 6 30 40 P. borceae 4 20 Length (mm) Egg (num/ind.) 10 20

2 Ovigerous female (%) 0 0 0 AM J J A S OND J FM AM J J A S OND J FM 2001 2002 2001 2002 12 25 100 F = 23.19, df = 11 10 20 80 8 15 60 6 10 40 P. maeoticus

Length (mm) 4 Egg (num/ind.)

5 20 Ovigerous female (%) 2

0 0 0 AM J J A S OND J FM AM J J A S OND J FM 2001 2002 2001 2002 Figure 4: Continued. International Journal of Zoology 5

16 250 100 F = 13.67, df = 12 14 200 80 12 10 150 60 cuda 8 6 100 40 Length (mm) G. aequi a 4 Egg (num/ind.) 50 20 2 Ovigerous female (%) 0 0 0 AM J J A S OND J FM AM J J A S OND J FM 2001 2002 2001 2002 250 100 16 F = 8.91, df = 7 14 200 80 12 150 60 10 8 100 40

6 Egg (num/ind.) 50

Length (mm) 20 O. acuminatus

4 Ovigerous female (%) 2 0 0 0 AM J J A S OND J FM AM J J A S OND J FM 2001 2002 2001 2002 Ovigerous female (%) Mean length (+Sd) Mean fecundity (+Sd)

Figure 4: Mean length (mm), fecundity (egg/ind.), and frequency of ovigerous female for each species during April 2001 to March 2002.

Table 1: Sampling localities for amphipods of the present study.

Studied specimens Species Sampling site Position Altitude Sampling method∗ number Gammarus lacustris Neur Lake From substrate by 38◦ 00 N, 48◦ 35 E 2500 m 1158 G.O. Sars, 1863 (3 points) E.d Gammarus Gorigol Wetland From aquatic plant paricrenatus 37◦ 54 N, 46◦ 42 E 1330 m 1465 (3 points) by H.s Stock et al. 1998 Springs; Hiran 38◦ 24 N, 48◦ 44 E From stream Gammarus komareki Navrud 37◦ 42 N, 48◦ 51 E 1200 to 1700 m 2924 vegetation and Schaferna, 1992 Sefidab 37◦ 00 N, 50◦ 18 E detritus by H.s Kojor 36◦ 23 N, 51◦ 43 E Gammarus Gorgan Bay From edge aquatic aequicauda 36◦ 50 N, 53◦ 45 E −10 m 1215 (4 points) plant by H.s Martynov, 1931 Obesogammarus Anzali Wetland From aquatic plant acuminatus 37◦ 29 N, 49◦ 21 E −5 m 518 (4 points) by H.s Stock et al. 1998

Pontogammarus maeoticus (Sowinsky, 1894) Caspian sea shore; 2014 Astara, 38◦ 26 N, 48◦ 53 E From substrate Sefid Rud estuary 37◦ 27 N, 49◦ 55 E −10 m by E.d Pontogammarus Kelachi 37◦ 05 N, 50◦ 26 E borceae 907 (Carausu, 1943) ∗ E.d.: Ekman dredge and H.s.: handle sieve. 6 International Journal of Zoology

30 210 P. maeoticus O. acuminatus 180 25 y = 1.57x − 5.73 y = 13.96x − 118.74 R2 = . 150 R2 = . 20 0 254 0 585 P = . E − P = . E − -value 1 4 8 120 -value 8 5 7 15 Egg Egg 90 10 60 5 30 0 0 4 681012 14 16 18 4 681012 14 16 18 Female size Female size (a) (b)

80 240 P. borceae G. aequicauda 70 200 y = 4.67x − 24.32 y = 11.50x − 63.23 60 R2 = . 0 442 160 R2 = 0.508 50 P-value = 8.9E − 19 P-value = 9.7E − 29 120

40 Egg Egg 30 80 20 40 10 0 0 4 6 8 10 12 14 16 18 4 681012 14 16 18 Female size Female size (c) (d)

35 25 G. komareki G. lacustris 30 y = 1.93x − 6.1 20 y = 0.38x +5.3 25 R2 = 0.162 R2 = 0.015 P = . E − 20 -value 2 8 20 15 P-value = 0.42 Egg Egg 15 10 10 5 5 0 0 4 681012 14 16 18 4 681012 14 16 18 Female size Female size (e) (f)

30 G. paricrenatus 25 y = 1x +2.8 20 R2 = 0.052 P-value = 0.449 15 Egg 10

5

0 4 6 8 10 12 14 16 18 Female size (g)

Figure 5: Linear regression of egg number in brood pouch with female size for each species. International Journal of Zoology 7

Table 2: Mean length of male and female specimens for each species.

Min. and max. length of Species Mean length ± SEa t-valueb Sex ratio (F/M) ovigerous female Gammarus lacustris F = 12.42 ± 0.12 (321) 2.26∗ 1 : 1.5 8–16.7 G.O. Sars, 1863 M = 12.87 ± 0.16 (397) Gammarus paricrenatus F = 11.01 ± 0.13 (274) 5.43∗ 1 : 1.2 10–14.5 Stock et al. 1998 M = 12.04 ± 0.14 (350) Gammarus komareki F = 7.65 ± 0.04 (876) 16.64∗ 1:1.2 5.5–12 Schaferna, 1992 M = 8.71 ± 0.05 (1093) Gammarus aequicauda F = 9.94 ± 0.11 (228) 6.74∗ 1:1.2 5.4–14 Martynov,1931 M = 10.94 ± 0.16 (274) Obesogammarus acuminatus F = 11.03 ± 0.21 (120) 1.17 1 : 1.2 7.2–16.7 Stock et al. 1998 M = 11.43 ± 0.26 (109) Pontogammarus maeoticus F = 8.49 ± 0.09 (334) 5.73∗ 1 : 2.2 6.1–12.8 (Sowinsky, 1894) M = 7.89 ± 0.05 (641) Pontogammarus borceae F = 8.62 ± 0.10 (236) 0.23 1 : 1 5–13.3 (Carausu, 1943) M = 8.60 ± 0.09 (214) a The measurements did not include newly hatched and juvenile individuals. The numbers are examined presented in the parenthesis. bt-test for equality of mean length between sexes. ∗Significant difference at the .05 level.

30 Table 3: Pearson correlation of mean egg number with percentage of ovigerous females during different months for each species. 25 Species Correlation value (Sig. level) 20 G. paricrenatus −0.22 (0.78)

SD G. lacustris 0.97 (0.17) ± 15 G. komareki 0.15 (0.65) P. borceae −0.02 (0.96) Mean 10 P. maeoticus 0.65 (0.04)∗ G. aequicauda −0.46 (0.13) 5 O. acuminutus −0.41 (0.42) ∗ 0 Correlation is significant at the .05 level (2-tailed). Anzali Caspian Gorgan Gorigol Neur Springs Wetland sea shore Bay Wetland Lake Station females and brood size of P. maeoticus were observed in mid- spring (Figure 4). The maximum egg number per female Water temperature ( ◦C) was observed in G. aequicauda (225 eggs), and its ovigerous Dissolved oxygen (mg/L) female percentages were larger in spring than in winter while the mean brood size was vice versa (Figure 4). The mean Figure 6: Water temperature and dissolved oxygen in sampling sites number of eggs of G. lacustris and P. borceae was 10.2 ± 5.2 during April 2001 to March 2002. and 14.9 ± 13.1, respectively. According to Figure 5, body length was linearly signifi- cantly correlated with number of eggs per female for species Various lengths of G. komareki (Figure 2)werepresentin of O. acuminatus (r = 0.765, P<.01), G. aequicauda (r = all months of the year but the maximum and minimum 0.710, P<.01), P. maeoticus (r = 0.504, P<.01), P. borceae mean lengths were observed in August and December, resp- (r = 0.664, P<.01), and G. komareki (r = 0.404, P<.01). ectively (Figure 2). The least percentage of ovigerous females There was no significant correlation between egg number was also distinguished from August to November, increased and individual length for G. lacustris (r = 0.122, P>.1) its trend in the following months, and peaked in spring and G. paricrenatus (r = 0.23, P>.1). Only in P. maeoticus (Figure 4). did the mean number of eggs correlate to the percentage of Overall, G. aequicauda and O. acuminatus showed the ovigerous females (Table 3). highest fecundity with mean egg numbers of 37.7 ± 31.1 Results of habitat characteristics show that Neur and and 49.8 ± 39.9, respectively, while G. komareki and P. Gorigol freshwater Lakes are located at high altitude (more maeoticus had a few eggs per female with 8.8 ± 5.0and than 1330 metres above sea level) and their salinities are 0.3 8.8 ± 5.3, respectively. The greatest percentages of ovigerous and 0.7 ppt., respectively, (Table 4); the water temperature 8 International Journal of Zoology

Table 4: Some abiotic characteristics of the habitats. Parameters Neur Lake Gorigol Wetland Springs Gorgan Bay Anzali Wetland Caspian sea shore DIN (mg/L)∗ 0.36 0.69 0.57 0.19 0.67 0.3 TN (mg/L)∗ 1.87 1.42 0.84 1.52 1.34 0.71 DIP (mg/L)∗ 0.16 0.05 0.07 0.04 0.08 0.07 TP (mg/L)∗ 0.38 0.10 0.11 0.14 0.2 0.11 Ca (mg/L)∗ 50 22 57 331 99 216 Mg (mg/L)∗ 15 21 11 661 143 397 Total Hardnes s (m g/L) ∗ 131 141 195 3620 774 2293 Range of pH 8.4–8.9 9.1–10.9 5.8–10.4 7.6–8.7 6.8–8.3 7.8–8.5 Range of Salinity (ppt) 0.2–0.3 0.4–1.4 0.2–0.4 5.6–22.6 0.6–7.5 3.2–10.7 ∗ From a single sampling during October 2001. in Gorigol varies between 0 and 30◦C which is slightly size classes and the ovigerous females, observed in many higher than that in Neur (0–23.6◦C). The oxygen level is species [18]. The population of G. komareki showed an also higher in Gorigol than that in Neur (Figure 6). The iteroparous annual life cycle where juvenile recruitment pH in Gorigol is more alkaline than Neur (Table 4). The peaked in winter and mid-spring. This characteristic dom- coastal habitants (Astara, Sefid Rud estuary, and Kelachi), inated in G. aequicauda populations during spring. The re- Anzali Wetland and Gorgan Bay are −10 to −5 meters productive pattern of P. maeoticus showed two seasonal peaks below sea level. The Gorgan Bay, is the most saline (15.8 ± in January and June-July, which was previously observed [8]. 5.7 ppt) followed by coastal area (7.1 ± 4.15 ppt) and Anzali This was also recorded for the north Caspian Sea population Wetland (3.2±2.8 ppt). The temperature (Figure 6)inAnzali of P. maeoticus [2]. Three peaks of ovigerous females of Wetland 20.2 ± 7.6◦C was higher than that in the coastal two sandhoppers which are indicative of more than one area (18.2 ± 7.8◦C); the pH values in the coastal area generation in a year were observed by Charfi-Cheikhrouha and Gorgan Bay were relatively similar (about 8.3) but in et al. [19], and they suggested that this continuous breeding Anzali Wetland the pH was barely neutral (7.7) (Table 4). activity occurs in the southern geographic distribution The oxygen level in Anzali Wetland was lower than that of populations. More generations per year of Calliopius in coastal area and Gorgan Bay (Figure 6), and dissolved laeviusculus have been observed in the southern populations, inorganic nitrogen (DIN) in Gorigol and Anzali Wetlands rather than a single generation in the northern ones [20]. total nitrogen (TN) in Neur Lake and Gorgan Bay had the Individuals of G. locusta produce two generations each highest concentrations. Compared to other sites (Table 4), year,inwinterandsummer[21], while Jazdzewski [22] Neur lake showed the most phosphorous components consist reported production of three generations in spring, summer, of total phosphorus (TP) and dissolved inorganic phos- and autumn each year for this species. According to Steele phorus (DIP). The springs Hiran, Navrud, and Kojor were and Steele [20], temperature shows marked influence on life mainly located in mountainous areas well above sea level; and reproduction of individuals. The higher temperature their salinities are low so they are almost freshwater habitats. provides favourable condition for faster growth and devel- The temperature is relatively low (12.8 ± 5.4◦C) with respect opment resulted in occurrence of multiple generations annu- to other habitats. Oxygen concentration is high (10.9 mg/L) ally. This was confirmed with G. komareki, P. maeoticus, and and their pH is almost neutral (7.74). G. aequicauda in this study. Moreover the low temperature variation in springs and small streams (Figure 6)caused 4. Discussion the continuous reproduction in G. komareki. Steele and Steele [17] also showed that high summer temperatures, The sex ratio and domination of males in most adult pop- particularly promote rapid growth of G. dubeni and allow ulations in this study probably resulted from better sur- a second generation to breed. Showing continuous breeding vivalandfastergrowthrate.Thisisalsoobviousintheir same as other species [1, 4], many peaks of reproductive size difference (Table 2). In most gammarid amphipods, activity in this species support the idea of multiple breeding sexual dimorphism is observed and this was previously during their life. proved in G. chevreuxi [1]. However biotic and abiotic Conversely, both G. lacustris and G. paricrenatus have a environmental factors have an effect on sex ratio as the study simple annual breeding cycle, with a reproductive peak in by Steele and Steele [17]onGammarus dubeni showed that May to July (Figure 2). The water temperature varies widely low temperature results in males, high temperatures produce between the habitats (Figure 6) where the high latitudes females, and during the rest of year the sex ratio is usually and low temperatures of winter result in slow growth and equal. development and the production of a few or one generation In this study Gammarus komareki and G. aequicauda de- per year. Similarly, in the life cycle of Synurella ambulans monstrated continuous breeding throughout the year, as from central ponds of Poland which were covered with indicated by the number of juveniles present in the smaller ice during winter, hatching occurs in summer, individuals International Journal of Zoology 9 mature in the following spring, and in August and September in burrow mostly immobile, and feeding on interstitial the parents are completely replaced by a new generation microflora and microfauna resulted in reduction in body [23]. Other species [24], for example, Gammarus setosus,that size in infaunal benthic animals [3]. In this study, the adapted to the low temperatures of northern environments pattern of increasing brood size with body size (Figure 5) showed a single brood produced per year. According to is probably a general trend in malacostracan Crustacean Sainte-Marie [5], the cold-water animals are lager and live including as stated by Nelson [3]. Several studies longer but show late maturity. These are breeding once on life cycle of freshwater gammarids revealed a significant a year and produce few broods during lifetime. As high correlation between female length and the number of eggs latitude amphipods can have resting stages, it is possible that [23, 29]; our finding also demonstrate similar relationships the immature specimens of G. lacustris and G. paricrenatus between female size and egg numbers for G. aequicauda, entered the resting stage directly in autumn and early winter O. acuminatus, P. borceae, G. komareki, and P. maeoticus. rather than producing a brood immediately. However, in G. lacustris and G. paricrenatus, the number The reproduction indices of G. lacustris and G. paricre- of eggs did not significantly increase with the length of the natus suggest the K breeding strategy, similar to Arctic and female. Synurella ambulans also exhibited a similar pattern Antarctic benthic such as Onisimus litoralis that [23]. have a long life cycle, larger eggs, and also larger female size According to these field observations and the supple- [25]. mentary laboratory experiments [6] it was concluded that From the habitat characteristics it is understood that high four species, P. maeoticus, P. borceae, O. acuminatus, and G. oxygen level is critical for survival of G. komareki and Ponto- aequicauda, seem to be good candidates for potential use in Caspian species while G. paricrenatus prefers habitats with a warm water fish farms. However, a subsequent study [30] higher pH, and low salinity. This species is able to tolerate produced negative results as Amphipoda replacement in fish high seasonal temperature and high daily oxygen variations culture ponds was not satisfactory with most animals dead whereas G. komareki lives in habitats with very low salinity, within a few days. The hydrochemical parameters including weakly alkaline pH and highly oxygenated water (Table 4 and poor oxygen concentration and very high nutrient levels Figure 6). The high values for phosphorus and nitrogen in were the factors responsible for mortality of specimens. In Neur Lake (Table 4) can be compared with other localities conclusion, future work is needed to determine whether P. from previous works [26], which showed that G. lacustris was maeoticus can adapt to fully freshwater environments. present in 53 lakes with pH > 6.3 and absent in highly acid, eutrophic, or polyhumic lakes. Two other benthos species, Pontogammarus maeoticus, Acknowledgments and P. borceae live in brackish water with salinity of 7.1 ± 4.1 ppt, fine sandy shores, well oxygenated water, and weakly The authors are grateful to H. Khodaparast Sharifi who alkaline pH (Table 4). According to Kasymov [27], P. mae- provided useful comments on an earlier draft. The study was oticus migrates to a depth of two to three metres when supported through project no. 79-0710340000-04 from the temperatures fall below a certain limit. Ovigerous females Iranian Fisheries Research Institute, and the authors would begin to appear at 8.2◦C in March and begin to move to like to thank all persons responsible especially A. Danesh shallower water (one to two metres) when the temperatures the previous Vice President of the Inland Water Aquaculture reachd 17.8◦C in October in the southern region of the Research Centre. Caspian Sea [27]. In this study small P. maeoticus was observed from November to February when the temperature was below 12◦C. References The common Mediterranean intertidal species G. aeq- uicauda lives in a wide range of salinity between 5.6 and [1] M. D. Subida, M. R. Cunha, and M. H. Moreira, “Life his- 22.6 ppt in Gorgan Bay. According to Mirzajani et al. 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